Recently, organic EL display panels are gaining popularity as display devices. A typical organic EL display panel includes a substrate and organic EL elements disposed on the substrate. An organic EL display panel realizes high visibility and high shock resistance, because the organic EL elements included therein have high visibility for being self-luminescent and have high shock resistance for having a fully solid-state structure.
An organic EL element is a current-driven light-emission element. An organic EL element typically includes an electrode pair composed of a pixel electrode and a common electrode, and a plurality of functional layers that are layered between the pixel electrode and the common electrode. The functional layers include a light-emission layer that emits light by utilizing electro-luminescence occurring when carriers (holes and electrons) recombine therein.
In the manufacturing of an organic EL display panel, a foreign particle of extremely small size, such as dust, may adhere to a surface of an electrode or a functional layer. Also, resist defect may result in an electrode or a functional layer having a surface with local level unevenness. When a functional layer is formed above the substrate/functional layer in such a state, the functional layer above the electrode/functional layer may have relatively small thickness at a certain area thereof. Further, there may even be cases where the functional layer above the electrode/functional layer is not formed at a certain area. Here, an area of an organic EL element of an organic EL display panel where a functional layer has relatively small thickness compared to other areas or where a functional layer is not formed, is referred to as a defective area. Such a defective area may result in forming of a bright spot, and may ultimately result in forming of a dark spot in the course of time. A bright spot is an organic EL element having higher brightness than other organic EL elements, and is formed by current flowing in a concentrated manner through the defective area. A dark spot is an organic EL element whose light-emission layer has lost its ability to emit light due to a short circuit being formed between the pixel electrode and the common electrode. A bright spot becomes a dark spot in the course of time because current flows through the defective area (i.e., the bright spot) in a concentrated manner and the degradation of the defective area is accelerated.
In view of such problems, there is a conventional technology of preventing the occurrence of a dark spot by forming an insulative film on the defective area and thereby suppressing the flow of current through the defective area. In specific, the insulative film is formed by applying electrically non-conductive (i.e., electrically insulative) material in a fluid state over the defective area. Patent Literature 1 discloses one example of such technology.
Further, one conventional method suitable for forming such an insulative film with respect to the defective area, which typically has an extremely small size of around 0.5 to 10 μm, is needle application. Patent Literatures 1 and 2 disclose examples of needle application.